Motor-controlling mechanism.



PATENTED JAN. 7, 1908. H. W. CHENEY.

MOTOR CONTROLLING MECHANISM. APPLICATION FILED JUNE 8. 1906.

3 SHEETS-SHEET 1.

INVENTOR WITNESSES He bert WCheney ATTORNEY PATENTED JAN. 7. 1908.

H. W. CHENEY. MOTOR CONTROLLING MECHANISM.

APPLIOATION FILED JUNE 8.1906.

3 SHEETS-SHEET 2.

Vv e n e h C t r e m e H INVENTOR WITNESSES ATTORNEY 'IBWER warm, 5;342

PATENTED mm"), 1908.

H. W. CHENEY. MOTOR CONTROLLING MECHANISM.

APPLICATION FILED JUNE 8 1906.

3 SHEETS-SHEET 3.

TORNEY INVENTOR Herbert When QQQQQQQQ ELDQQ UNITED STATES PATENr oFFroE.

" HERBERT W. CHENEY, or nonwoon, onro, ASSiGNOR 'ro atms-cnatnnns OOMPANY,'A

I \To all whom it concern:

" structure of the r rings when the motor is runnin normally.

CORPORATION OF NEW JERSEY, AND THE BULLOCK ELECTRIC MANUFACTURING COM- PANY, A CORPORATION OF OHIO. I

" MOTOR-CONTROLLING monamsm.

Specification of Letters Patent. Patented Jan. 7, 1908.

No. 876,981. 7 Application filed Jane's. 1%?06- Serial Rio. 820.757.

the combination with an induction motor, of Bet known that I, HERQERT W. CHENEY, a rheostat in the rotor circuit thereof, means citizenfoftheUnitedwstatesfresidin at Nor which in one position short-circuits the rowood, in the county of-Hamilton and State of. tor windings internally, and electromagnetic Ohio, have invented certain new and useful means for'automatically movingsaid short- Improvements in Motor-Controllin Mech' circuiting .means" into operative position anisrn, of which-the.- following is a in I, clear, when the rheostat is moved into its position and exact specification of lowest resistance, and for automatically e0 .My in'ventionrelates to starters fofelecopening said short-circuit when the .rheostat trio motors,. andrnore particularlyto resistis moved out of such position; 'j i 0 ance starters for induction motors. 'w h In another aspect my invention comprises- 'Heretofore induction motors have beerian induction motor, a magnetically operated, made with a starting resistance withinthe -switch for admittingcurrent thereto, a starta rotor, in order to avoid the rubbi'ngoontact' ing resistance arranged tobe included-in the between the collecting brushes and the s'liprotor 'circuit ot the inotor', and connections jgwhe'reby the operating magnet of the current This involves a ve'ry'eomplicated and bulky admittingswitch oanbeei'iergized only when Ithasals'o been prothe starting resistance is fully in circuit. posed to have the startin fresistance exteri r In still' another aspect my invention con1-. nal. to the rotor and conneeLmLLherto by risesQfin an induction motor, a rotor having slip irings. Thisallows the rotorto hemits windings connected to slip -1ings,'and lified in Structure and diminished in size, poweF-operated means for short-circuiting ut has-the disadvantage-of a permanent .said'slip-rfilgsr'fl i sliding-contact at the slip-rings.

1' V Ina more specific-aspect, my invention One of the objects of my'invention is to comprises in an intiuction motor, a rotor provide means whereby the starting resisthaving its windings'connete d to slip-rings," anceanay beoutside of the rotor, but the electrically-operatedmeans for short-circuitfinal short'circuit may take.- place within the ing said slip-rings, and a master controller rotor. By this I am enabled toavoid the dis.- for Saidele'ct'rically operated means.

advantages 'due on the.one hand to the in From another point of view, my invention crease in size and complication of the rotor comprises a drumcontroller and a rectilin- .when the resistance is internal, and on the' earslide rheostat mechanicallyconnected to "other hand those due to theL-slidin contact operate together; or -more specifically, the

at'the slip-rings afterfthe motor has been combinationol'. an induction motor, a magstarted. I y I neticallyoperated switch for admitting cur- Another object of m invention is to prorent to the primarv element thereof, a rect-ividecertain 'eleotrica interlocks for 'pre linear-slide rheostat connected to the secondventing the starting of the motor wher any .ary element of said motor, adrumcontroller, of the controlling devices are inii iiproper a single operating devicemechanicallyconposition for such starting. nected to the rheostat andjdruin'controller A further object of my invention is to proto in partmovement thereto, mkete'ctii'tfil vide a' novel form of rheostat and actuating connections for the drum whereby the operatmechanism therefor. ing .magnetfof the current admitting switch Anti' further object of m invention is to canbe energized onlywhen-the rheostat is in ermit a romote'control of t e short-circuitposition otlughestresistance.

' ing device. 1 w Froiitstill another point of view my inven- In one of its my invention comtion comprises a rheostat having its contact prises an induction motor. an external re sistsurfaces downward and-immersed in oil; or ance in the secondarycircuit-thereof, and more specifically, the combination, in a con means within the motorfor short-circuitingtrollingdevice', of a series of contacts having said resistance. Q p their contact surfaces downward, a earriape More specifically my invention comprises carrying c y spring-pressed into slidin -engagement with said contact surfaces, an arranged to connect different contact surfaces together to vary the resistance of the rheostat, and a re.- movable tank of oil in which the carriage,

A contact fingers and contact surfaces are immersed.

' Other features of my invention will appear from the following description in connection with the accompanying drawings, and will be specifically pointed out in the claims.

' controller. Fi

Figure showing my invention in connection with a rectilinear-slide starting rheostat. Fig. 2 is an elevation showing the structure of a rectilinear-slide starting rheostat arranged to be operated by a rotary drum controller. Fig. 3 is a longitudinal section through the drum the drum with the circuits control ed thereby. Fig. 5 is a section on the line 55 of Fig.

"'"tion'. a section on device. a

- 'rent motor, here 2, with some ofthe parts. artially sectioned on-other lines to better show the constructhe line 6-6 of Fig. 2. ig. 7 is a sectional view of one-oi the operating magnets of the short-circuiting In the drawings A is an alternating curshownas' a rotor-woun induction motor, which .is supplied with current by the mains 1, 2 and 3, through-the switch i. This switch is biased toward ofi position by spring 5, but may be moved into on position'by solenoid 6, inwhich latter positionit is held by la'tch 7 until such time as the latch is released by the energization of the solenoid 8. The c rcuit of this solen- =main 3.

motorA is connected through shown as star connected to correspond with the connections of the rotor windings. This resistance may be delta-connected if the rotorwindings are so connected, the two-generally corresponding. This resistance can be varied by means of a sliding bar 14, movable, by a handle 14', over the contacts 40.

Within the slip-rings of the rotor is a power-operated device 15 for internally short-circuiting the rotor windings. This device ma be of any desired construction,- but shoul be, as shown, so arranged that it can rotate with the sli rings. This device" -is movable along the s aft of the motor A,

v and in' its inner position connects or bridges the slip-rings 12 to internall short-circuit the rotor win by simu taneously engaging the inwar projections 16 from said' its outer position the device 15 is super 1 is a partly-diagrammatic view,'

4 shows a development of outv of engagementwith the projections L5 and. the internal short-circuit of the rotor 1S by magnets 17 and 18 respectively, energized ".by a battery or other source of current 19 and-underthe remote control of the master c ontroller. The structure of these magnets will be hereinafter ex lained. The circuits of the magnets 17' an 18 are closed during the movement of the resistance-varying bar or master controller 14-. by an extension 20 therefrom. As the bar 14 is moved between the position of highest resistance and next position thereto,.or between the posi-. .tion of lowest resistance and the next posipleted by extension 20, to .-cause it to move the device 15 out of short-circuiting position should 1t be in such position; I As the resistance-varying bar 14 is moved into its-position'of'lowest resistance, the circuit of magit to move the device 15 into its short-circuiting or-bridging position. As the shortcircuiting device is moved into this osition, such movement breaks the circuit of magnet 17 at the switch 21. This remote control of the short-circuiting device is believed to be broadly new with me.

are wound for the same voltage, source of sup ly ma .be used'for all of said magnets, as s own diagrammatically in Fig. 4'. In. order to a complete the circuit of. 1 solenoid 6, it .is' necessary-that theresistance varying bar14 bein 'positioii 0, 'i. 0., its position of highest resistance, and that the short-circuiting bridging position, thus closing the switchi23. If such is the -condition, the? circuit of magnet 6 may be closed by the .push button '24. 11f suchis not the condition, it is impossible to close the main switch 4, and -therefore current primary member of motor A u ess all of the resistance 13 is includedin the secondary circuit thereof by reason of the-bar 14 being in its highest resistance position and the internal s ort-circuit of the rotor winding being open.

The operation ofjthe system above de-.' scribed is as follows: With the parts in the .positionshown, the current-admitting switch As the-motor5i be t9 increase-in speed the resistance 13 out, of the rotor. circuit of saidz motorm As the resistance-varying bar broken. This short-circuiting device is nov able into and out of short'circuiting position The solenoids (Sand 8 are suppliedby & 60111111011 the ' tion thereto, thecircuit of magnet 18' is com-' 7 net'17 is completed by xtension20', to cause batte 22 which ishere shown as being dis tinct om the. battery 19. 'It is obvious, however, thatif the magnets 6, 8, 17 and 18 cannot be sixipplied to the 4 can be closed; by pressing the button 24.

is moved in this direction, the magnetv 18 is energized twice 6. e., as bar 14 passes from positions to 1, and from 7 to 8, but does nothing at this time, because the short-cm cuiting device 15 is already in open position.

' merit of the short-circuiting device 15 opens the circuit of magnet 17. Should an overload occur, the solenoid 10 is energized sufficiently strongly to raise its switch, thus closing the circuit of the solenoid 8 to tripswitch 4 and cause the motor to stop. The motor cannot be started again until the bar 14 has been moved into its extreme left-hand position, during which movement the mag net 18 is energized to move the short-circuiting device 15 out of bridging position. If at any time the bar 14 is moved out of position 8, it at once, by its exten sion 20, closes the circiiit of magnet 18 to open the internal short-cir'cuit'of the rotor windings.

If, desired, one set of the contacts with which the extension 20 engagesto close-the circuit of magnet 18 may be omittedythe two sets bein provided merel for the better insuring of t e movement 0 the device 15 out of bridging position when'the arm 14 is magnet 17 is energized as tlt'e controller goes moved to the it. There maybe'a handle for o crating the shortcircuiting devicemanually if desired.

In Figs. 2 to 6 is shown an arrangement in which the resistance 13 is varied by means of a speclall-y constructed rheostat, this rheostat being operated in conjunction with a rotary master controller 26 of the drum type,

. by means of a singlehandle 2-7. A develop ment of this drum controller is shown in Fig. 4 together with some of the controlling circuits. These controlling circuits are here 50- shown as being supplied by'a single battery 28, instead of by the separate batteries 19 and 22 of Fig. 1-, the controller closing the circuits in substantially the same manner asin Fig. 1 save that the magnet 18 is energized. when the controller is in position 7, and the from position 7 to position 8. 'With this arrangement, thei'e is no necessity for the switch 21, but there is the disadvantage that the circuit of magnet 17 'may not be closed sufficiently long to enable said magnet to perform its duty. It is obvious that the arrangement shown in Fig. 1 mav be varied to act as the controller shown in 4. and vice versa, and that separate batteries for the ance 13, which" is shown in Fig. 1.

sproci'ietwheel 30 on the shaft thereof, to a rock arm 31, upon a shaft 32.

Also mounted on tl is shaft are arms 33 connected by links 34 to a carriage 35 mountedon rollers 36 to run on trac'zs 37-. This carriage supports the bar 14 and is suitably insulated tnenefrom. On the bar 14 are mounted contact fingers 39, spring-pressed upwardly into sliding engagement with trze under surfaces of-contacts 40. The contacts 40 are properly connected, as-by connectors 40, to the resist- As the drum 26 is rotated, rectilinear movement is imparted to'carriage 35 vand'contact fingers 39 by means of sprocket wheel 30, chain 29,

rock arm 31, arms 33 and links 34. This movement cuts the'resistance 13 into or out of the motor circuit in the same manner as shown in Fig. 1. Surrounding the contacts 40, contact fingers 39, carriage 35 and run; way 37, is a tank containing oil in which said parts are immersed. The tank 41 is removabl f tened to slotted projections 42 on the MM; rheostat by swivel bolts 43, and is filled vith oil to the oildeyelf shown on the drawings. I

The magnets 17 and ,18 which operate the shor't-circuiting device'15 are identical in structure and are of. the iron-clad solenoid "tion 45 which extends into tiiecoils. In the inner end oQliis projection 45 is a steel plunger 46, pressed upwardlyby an adjustable spring -47. The'nmer surface of projection 45 has a facing 48 of non-magnetic material,

. through which the plunger 46 extends. The

core 49 0f magnet 17 has a steel plug 50 em bedded inits center, which engages with the is energized. his plunger 46 and plug 50 serv'esa threefold purpose: first, to take upthe shock of the hammer-blow when the core 49 reaches the end of its movement; second, .to allow the movement of the short-circuiting device to be completed when the magnet is energized, whatever the position of the motor shaft in its emtplay, but, after the ,magnet has been denergized, to return the ac'tuatingleveF of said device to such a position that the sides of t l egroove of the shortcircuitingdevicc will not come into contact with the pin in said le'ver during the end-play spring-pressed lunger 46 when the magnet of the shaft, the short-circuiting device being 3 fully opened, as the case may be; and third, by reason of the higher retentivity of the ,parts 46 and 50, to retain the core 49,. once it as been attracted, in said attracted position after the magnet 17 or lfi has been deenergized, these magnets thus having an electromagnetic actuating part and a permanently magnetic retaining part. The strucyso is identicalwith that of scribed. I Inftliis specification, the terms stationary rheostat or stationary resistance" are usedto denotea rheostat or resistance which is not mounted for rotation with the those above de- -rotor.- The terms internal connection,

internal short-circuit, etc. are used to denote a connection, short-circuit onthe. h'ke',

' 7.' In astarter for a rotor-wound inducwhich is made by means carried .b. the-r0 tating element of the motorvan not by brushes bearing on the outer surfaces. of; the

sli rings.

t is obvious that man modifications may be made in the details'o construction of the invention and are intended invention described above. All such rnodie fications come under the broad spirit of my the'following claims:

What I claim as new' and desire to secure by Letters Patent is: l I

1. In a starter for aninduction motor, the

combination with said motor, of a resistance 7 in the rotor circuit thereof, means for gradue ally cutting out said resistance, andmeans for internallyshort-circuiting the rotor wind-- ings effective when the resistance has-been fully cut-out. l v

2. In astarter for an induction motor, the combination-With said motor, of a starting resistance connected to the rotor slip-rings thereof, means for cutting said starting resistance out of circuit, and means for connecting the slip-rings internally, said last mentioned means being efi'ectivewhen the starting resistance hasbeen fully cut out.

3.A In a starter .for a rotorswound induction motor, the combination Withjsaid motor, of astarting resistance-connected to the.

'rotor slip-rings thereof, manually operatedmeans or gradually short-circuiting said starting resistance, and electrically operated; means for connecting said slip-rings inter nally when the starting'resistance has been fully cut out.

4. In a starter for an induction motor, the, combination with said motor, of a rheostat in the rotor circuit thereof, means for-shortcircuiting the rotor windings internally, and means fors operating said short-circuiting means when the rheostat is moved into' its position of lowest resistance, and for opening said short-circuit when the rheostat is moved out of such position.

5. In a starter for an induction motor, the combination with said motor, of a rheostat in the rotor circuit thereof, means which in one position short-circuits the rotor windings internally, and electromagneticimeans for moving said short-circuiting means into operative position when the rheostat is moved into its position of lowest resistance, and for opening said short-circuit when the rheostat is moved out of such position.

I necting means to connect t 7 mg means to connect t to be covered; by elf tween its position of highest resistance and rings, means for internally connecting t e slip-rings, and means for operaiiting said c1on-' e s p -rlngs w ien the rheostat is moved into its position of lowest resistance and for breaking such connection when the rheostat is moved into its position of highest resistance,

rings, meanslfor internally connecting tie slip-rings, means for operating said connecte slip-rings when the rheostat is moved into its position of lowest resistance, and for breaking such connection,

made whenever the rheostat is moved be the nextposition thereto.

tion 'motor,,the combination with said m0- tor;;of a stationary rheostat in the rotor circuit, means which in one position short-circuitstherotorwindings internally, and electromagnetic means for moving said short- 'circuiting *means into operative position when therheostat is moved into its position of lowest resistance and for opening said short-circuit, if closed, whenever the rheostat is r'novedbetween its position of highest resistance and the next position thereto.

- 9. In a's'tarter for an mduct'ion motor, the combination with said motor, ofa variable resistance in the rotor circuit, 'electromag- 'netically actuated means which in o ne position short-circuits said lotor winding internally, and connections whereby said shortcircu1ting means is. madeoperative when the Ina'starter for a rotor-wound in duc lOQ c variable resistance has been fully cutout and said short-circuit opened whenjthe resistance has been fully cut 1n.

" 10. In astarter for an induction motor, the combination with said motor, of a starting resistance in the rotor ci'rcui thereof, means for'bridging internallthe 'slip-rings of the rotor, electromagnets or moving said bridging means, into and out of connection with said slip-rings respectively, and con nections whereby the second ofsaid magnets is energized a'ssoon as the starting resistance hasbeen begun to becut out, and the first of said magnets energized when the starting resistance'is fully cut out.

1 1. In combination, an induction motor, a

magnetically operated switch for admitting current thereto, a starting resistance arranged to be included. in the secondary circuit of the motor,- and connections whereby the operating magnet of the currentadmit-' ting switch can be energized only when the starting resistance fully circuit.

12. In combination, an induction motor, a

magnetically operated switch for admitting current thereto a startin resistance ar-t resistance.

ranged to'be included in the rotor circuit of I the motor, connections whereby the operatlng magnet of the current-admitting switch can be energized only when the startin resistance is full in clrcuit, and an over oad magnet for tripping'the current-admitting switch when the current rises too high.

the rotor windings internally, and conneotrons whereby the magnet of the current-ad- 'mitting switch can be energized to close said I is in inoperative position.

13. In combination, an induct-ion motor, a magnetically operated switch for adnnttiug j current thereto,'a' 'statlonary starting reslstcurrent thereto, a starting resistance arranged to be included in the rotor circuit of I the motor, means which in its operative position short-circuits the rotor-windings internally, and connections whereby the operating magnet of the current-admittin switch can t be energized to close said swite l only when the starting resistance is fully in circuit and theshort-circuiting means is in inoperative posltion. I

14. In combination, an induction motor, a magnetically operated switch for admitting current 'thereto, a starting resistance arranged. to be included in the rotor circuit of the motor, means which in its operative position short-circuits the rotor windings internally, connections whereby the magnet of the current-admitting switch-can be energized to close said switch only when the starting resistance is fully in circuit and the short-circuiting means is in inoperative position, and an overload magnet for tripping the currentad'mitting switch when the current rises too high. I

15. .In combination, an induction motor, a magnetically .operated switch for admitting current. thereto, a stationary starting resistance arranged tobc'included in the rotor circuit ot' the motor, means for cutting out such resistance, which in its operative position short-circuits the rotor windings internally, and connections whereby the operating magnet of the current-atlmitting switch can be energized to close said switch only when the starting resistance is fully in circuit.

16. In combination, an induction motor, a magnetically operated switch for admitting current thereto, a stationary starting resist- I ance arranged to be included in the rotor circuit of the motor, means for cutting out such resistance, magnetically operated means which in its operative posit-ion short-circuits the rotor windings internally, connections said switch only when the starting resistance magnetically operated means i i g is fully in circuit, and an overload ma net for 1 tripping the current-admitting switc 1 when 1 the current rises too high.

17. in combination, an induction motor, a magnetically operated switch for admitting current thereto, a stationary starting resistance arranged to be ncluded 1n the rotor cucuit of the motor; means for cutting out such 18. In combination, an induction motor, a n'iagnetically operated switch for admitting ance arranged to be included in the rotor circuit of the motor, means for cutting out such resistance, magnetically operated means which in its operative position short-circuits the rotor windings internally, connections whereby the magnet of the current-admitting switch can be energized to close said switch only when the starting resistance is fully in circuit and the short-circuiting means is in inoperative position, and an overload magnet for tri )ping the current-admitting switch when t e current is too high.

19. In an induction motor, a primary member, a wound secondary member, means for short-circuiting said secondary member, and electromagnetic means for operating said short-circuiting means.

' 20. In an induction motor, a rotor havin its windings connected to slip-rings, an

power-cperated means independent of thes cod 0 the motor for short-circuiting.said s ip-rings.

'21. In an induction motor, a rotor having its windings connected to slip-rings, and electrically operated means for short-circuiting said sli rings.

'22. 11 an induction motor, a rotor having its windings connected to slip-rings, power operated means for short-circuitirig sald sliprings and a master controller forcontrolling the operation of said power-operated means in both directions.

23. In an induction motor, a'rotor having its windings connected to slip-rings, electrically operated means for short-circuiting said slip-rings, and a mastercontroller for said electrically operated means.

24. In con'ibination, an induction motor, an external resistance in the secondary circuit thereof, and magnetically operated magnetically operated means which in 1ts operative position short-circuits means within the motor for short-circuiting cuit thereof, means for gradually cutting out said resistance, and automatic magnetically operated means within the motor for short-clrcultmg said resistance.

7.727. In. combination,. a threehase indu tion motor, an external resistance connected r-to slip-rings of the rotor thereof,- and automatic magnetically operated means rotatable with said rotor for internally bridging said sli '-rings.

28. n combination, a three-phase induc tion motor, an external resistance connected to slip-rings of the rotor thereof, and automatic electrically operated means rotatable with said rotor for internally bridging said sli -rings.

29. In combination a three-phase induction motor,- n-externalresistance connected to the slip-rings of the rotor thereof, means for varying said resistance,"and automatic electrically operated meansf'rotatable with said rotor for internally bridging said sliprings. a I

30. In combination, an electric motor,- a

power-operated switch. for admitting current thereto, a drum controller for controlling said switch, and a rectilinea'r-sliderheostat for varying the resistance in the circuit .of one element ofsaid motor, said drum controller and said rheostat being mechanically connected to operate together.

3 1'. In combination, an electric motor, a

power-operated switch for admitting current thereto, a drum controller for controlling said switch, a. rectilinear-slide rheostatfor varying the resistance in the'circuit of one element of said motor, an operating handle, nd connections whereby both rotation of he drum and movement of the rheostat are obtained by moving saidjhandle.

32. In combination, an electric motor, a

magnetically operatedswitch for admitting big est resistance.

. 33. In combination, an induction motor, a magnetically operated switch for admit ting current to the rimary element thereof,

a rectilinear-slide r 'eostat connected to the secondary element of. said motor, a drum controller mechanically connected to the rheostat to impart movement thereto, and electrical connections for the drum whereby the operating magnet of the current-admitting switch can be energized only when the rheostat is in position of highest resistance.

34. In a rheostat,ua plurality of sets of "resistance sections, a set of'contacts for each set ofresistance sections, the surfaces of said contacts being downward and immersed in oil, and a relatively movable bridge rheostat and ing member in'sliding engagement with said contact surfaces and arranged to connect corresponding contacts of the various sets together.

35. In combination, a rheostat and a controlling drum arranged to be operated together, and means controlled by said 0011'-' trolling drum for cutting out said rheostat. 36. In combination, a rectilinear-slide rheostat and a rotatablewgntrolling drum arranged tobe operated toge her, and poweroperated means controlled "by said controlling. drum for shortscircuiting said rheostat.

37. In combination, an induction motor, airheostat for the'secondary circuit thereof,

'a controllingdrum, a common operating means for said drum and rheostat, and means controlled by said drum, for cutting out said rheostat.

. l 38. In combination, a device for internally .short-circuiting the rotor windings of an induction motor, and a magnet for operatingsaid device, said magnet having a springpressed plungerin one of its relatively movable parts with which the other of saidparts 'engages and acting, after the magnet is deenergized, to return the. actuating mechanavoid friction duringthe end play of the Totor.

39. In combination, a device for internally short circuiting the rotor windings of an in- .duction motor, and a magnet for operating said device, the soft iron, relatively movable parts of said magnet havingsteel plugs which .retain the short-circuiting device in position after the magnet is deenergized.

40. In combination, a device for internally short-circuiting the rotor windings of an in duction motor, two magnets for respectively moving said device into and out of short-cirism ofthe short-circuit'ing device slightly to cuiting positi8h,each of said magnets having a spring-pressed plunger in one of its relatively movable parts for contact with the other of said parts and acting, after the mag nets are' deenergized, to return'partly the actuating mechanism of said short-circuiting device to avoidfriction during end play of the rotor.

41. In combination, a device for internally short-circuiting the rotor windings of an induction motor, and two magnets for respectively moving said device into and out of short-circuiting position, the soft'iron, relatively movable parts of said magnets having plugs of higher retentivity to retain the short-circuitmg device in position after the operating magnet. is decnergized.

42. In'com ination, a device for internally bridging the slip-rings of a rotor wound induction motor, a magnet for operati said device, and a switch in the circuit 0 said magnet which is automatically opened by the operation of the bridging device.

Correction in-Lett'ers Patent No. 875,98L-

43. In combination, a device for internally In testimony whereof I affix my signature bridging the slip-rings of arotor-Wound inin the presence of two wltnesses. duction motor, two magnets for movingusaid HERBERT W CHENEY device into and out of brid ing position, and p a switch in the circuit-of t e magnet which moves the device into bridging position which is automatically. opened by such movement.

Witnesses: GEO. B. SCHLEY, FRED J. KINSEY.

' It is herebj certified that in Letters Patent No. 875,951, granted January 7, 1908, upon the application of Herbert W. Cheney, of Norwood, Ohio, for an improvement in Motor-Controlling Mechanism, an error appears in the printed specification requiringcorrection, as follows: In line 122, page 3, after the'word being, the words this correction therein that the same may conform to the record of the case in the Patent Office; v I i 0 I Signed and sealed this 28th day of January, A. 1);, mos. [sEAn] o. o. nILLINGs,

Acting Commissioner of Patents.

. fully closcd or shonld be inserted; and-that the saidLetters Patent should be read with 

